SCP: Verification of Simulation Software

In In 1996, a Group of Experts was created with the aim of developing a
Standard Computation Program (SCP) to determine whether a non-GSO Mobile
Satellite Service (MSS) system would need to coordinate with existing Fixed
Service (FS) systems.

The Group of Experts produced an information document for the February 96
meeting of ITU-R Working Party 8D, which was copied in a liaison statement to
ITU-R WP 9D (meeting at the same time). It was clear that both groups had
interests in the development of the SCP and on May 1st 1996 a Joint Rapporteurs
Group (JRG 8D/9D) was set up to develop, among other things, the SCP
methodology.

The need to develop an SCP was a consequence of the filings of many non-GSO
MSS systems in the 1 – 3 GHz bands. Detailed coordination between each MSS
systems and all potentially affect FS systems would be an enormous task, and
some pre-coordination filter was needed.

In anticipation that some simulation would be needed, MSS organisations had
been producing simulation software for some time.

By this time Visualyse Professional was also well enough developed to be
useful for coordination and a candidate implementation of the SCP. In fact
Visualyse Professional was already the industry’s leading interference
analysis product, and was able to model accurately the MSS systems under
consideration.

The development of Visualyse Professional and the efforts of some MSS
operators in developing their own software meant there was enough experience
available to allow the JRG to move ahead quickly with its work. Transfinite
Systems staff had been involved in the development of methodologies for this
kind of simulation since 1992 and were key members of the JRG software experts
group.

Other than SCP, the JRG also addressed detailed coordination issues and in
October 1997 ITU-R Recommendation M.1319 was approved. Visualyse Professional
was specified in the JRG Chairman’s report as an acceptable implementation of
Rec. M.1319 in the context of Resolution 716.

The task of defining the SCP methodology proved to be quite difficult. The
point about the SCP is that it defines a "coordination trigger". If a non-GSO
MSS system does not pass the tests set in the SCP then further detailed
coordination under Rec. M.1319 is needed. The two competing parties in the JRG
wanted different emphasis in the SCP, for obvious reasons, i.e. the FS operator
wants to be certain that the worst case assumptions are used so that no systems
which could cause interference can pass the SCP tests. On the other hand the
MSS operator does not want to trigger every possible case, and thereby increase
the coordination effort needed many times.

The Recommendation that captures the SCP methodology (ITU-R Rec. M.1143) was
also approved in October 1997. Visualyse Professional was adapted to take
account of this Recommendation and subsequently submitted to the ITU-R for
accreditation, in response to an ITU circular letter (CR70), requesting
software from all administrations.

The validation and verification process continued in JRG 8D/9D. Visualyse
Professional was run for several test cases and the results compared to results
from other programs. Results obtained were in close agreement, leading the
chairman to conclude:

- the description of the methodology described in Rec. ITU-R M.1143-1 is
sufficient at this stage and that no further revisions are required;

So the methodology has been defined and, Visualyse Professional has been
shown to be compliant and in agreement with other simulations. Visualyse
Professional is the only commercially available package that has been tested
against Recs. M.1143 and M.1319 in this way.

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